Electrical machine and use thereof

ABSTRACT

The invention relates to an electrical machine of the transversal-flux type. The machine comprises a stator and a movable element. The stator has a plurality of stator elements with magnetic flux conductors and an electric winding extending in a closed winding path through each magnetic flux conductor. The movable element comprises a number of permanent-magnet members and is movable in relation to the stator along a movement path. The winding path comprises a first current-carrying section extending along the movement path. Each magnetic flux conductor forms, together with one of the permanent-magnet members, a closed magnetic flux circuit around said current-carrying section. Each permanent-magnet member comprises a primary magnet with a magnetic direction across the movement path. Adjacently located permanent-magnet members are separated from each other by an intermediate member comprising at least one secondary magnet that has a magnetic direction essentially across the magnetic direction of the primary magnet.

TECHNICAL FIELD AND BACKGROUND ART

The present invention relates to an electrical machine of thetransversal-flux type according to the preamble to claim 1 (seeWO01/78218 (ABB AB) and WO01/78219 (ABB AB)). The invention also relatesto a use of such an electrical machine.

Conventional electrical machines operate according to the so-calledlongitudinal-flux principle, which means that the magnetic flux plane ofeach stator element is parallel to the direction of movement of therotor. U.S. Pat. No. 5,177,142 (Von Zweygbergk) discloses an electricalmachine that operates according to the so-called transversal-fluxprinciple. This known machine comprises a rotating rotor with a numberof permanent magnets and a stator with a corresponding number of statorelements that are arranged in such a way that the induced magnetic fluxsubstantially follows a path perpendicular to the direction of rotationof the rotor. The known machine is characterized by a high power ortorque density, that is, a large power or a large torque in relation tothe volume or physical size of the machine is obtained. U.S. Pat. No.5,177,142 discloses rotating machines of the transversal-flux type.

WO01/78218 and WO01/78219 both disclose a linear electrical machine ofthe transversal-flux type. The known machine comprises a stator with aplurality of magnetic flux conductors and an electric conductor thatforms a winding extending in a closed winding path through each magneticflux conductor. The machine also comprises a movable element with anumber of permanent-magnet elements. The movable element describes areciprocating motion in relation to the stator along a movement path ina space with a finite length. The closed winding path comprises a firstcurrent-carrying section extending essentially parallel to the movementpath. Each magnetic flux conductor together with one of thepermanent-magnet elements forms a closed magnetic flux circuit extendingaround the current-carrying section. The magnetic flux conductors arearranged in an alternating order with respect to the direction of themagnetic flux in relation to the permanent-magnet elements and themagnetic flux circuit, respectively.

As mentioned above, transversal-flux machines are characterized by ahigh power or torque density, that is, the power or torque that may beobtained is great in relation to the physical size of the machine.Further, the power in a transversal machine, contrary to that of aconventional electrical machine, is directly proportional to the numberof poles of the stator and the rotor or the movable element. As shown inthe above-mentioned WO01/78218 and WO01/78219, a transversal machine maybe made very compact, that is, with a large number of poles in arelatively small machine. However, the high torque density of knowntransversal-flux machines is associated with a relatively low powerfactor, that is, both the machine and the control unit must be designedfor relatively great dimensional outputs compared with their activerated powers. The reason for the low power factor is that knowntransversal-flux machines have a relatively great leakage of themagnetic flux, which results in a weak magnetic coupling between thestator and the movable element or rotor. The magnetic leakage, which isof a certain magnitude in all types of electrical machines, means thatpart of the magnetic flux disappears from the imaginary magnetic fluxcircuit without performing any work. The leakage thus deteriorates theefficiency of the machine.

In the above-mentioned electrical machines of transversal-flux type,leakage may arise both in the stator and in the movable element or therotor. In the stator, leakage may arise between adjacent magnetic fluxconductors in those sections where the magnetic flux extends in oppositedirections in the adjacent magnetic flux conductors. In the rotor,leakage may arise between adjacent permanent magnets since these have amagnetic flux in opposite directions.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an electrical machineof the transversal-flux type with a high torque density and withimproved power factor, that is, with a small magnetic leakage.

This object is achieved with the electrical machine described in theintroductory part of the description, which is characterized in thatadjacent permanent-magnet members of the movable element are separatedfrom one another by an intermediate member that comprises at least onesecondary magnetic which has a north pole and a south pole and amagnetic direction that extends from the south pole to the north poleand essentially across the magnetic direction of the primary magnet.

With such a secondary magnet, the magnetic flux leakage in the movableelement between adjacent permanent magnets may be reduced bycompensating the secondary magnet for the leakage. The secondary magnetcreates an addition of magnetic flux from the rotor to the stator in amagnetic flux circuit and from the stator to the rotor in an adjacentmagnetic flux circuit. More exactly, the magnetic direction of thesecondary magnet may advantageously extend essentially parallel to themovement path. The movement path may be a straight or somewhat curvedline, along which the movable element moves, for example in areciprocating motion. The movement path may also consist of a circle,whereby the movable element rotates around a centre point.

According to another embodiment of the invention, each intermediatemember of the movable element comprises two secondary magnets. Thesecondary magnets of an intermediate member between the first and secondadjacent permanent-magnet members may then advantageously be arranged insuch a way that the first secondary magnet is in the vicinity of thenorth pole of the primary magnet of the first permanent-magnet memberand the south pole of the primary magnet of the second permanent-magnetmember and so that the second secondary magnet is in the vicinity of thesouth pole of the primary magnet of the first permanent-magnet memberand the north pole of the primary magnet of the second permanent-magnetmember. In this way, the magnetic flux at each permanent-magnet memberwill be concentrated at the two poles in a direction to or from themagnetic flux conductors of the stator.

According to a further embodiment of the invention, each intermediatemember of the movable element comprises a layer of a magneticallyinsulating material outside of the two secondary magnets. Such a layermay, for example, be formed from non-magnetic material, such asstainless steel, and contributes to prevent demagnetization of thesecondary magnets by so-called armature reaction.

According to still another embodiment of the invention, eachpermanent-magnet member comprises a first magnetic flux conductor on oneside of the primary magnet and a second magnetic flux conductor on theother side of the primary magnet. Further, the secondary magnets of anintermediate member between two adjacent permanent-magnet members mayadvantageously be arranged in such a way that the first secondary magnetextends between said first magnetic flux conductor of the twopermanent-magnet members and so that the second secondary magnet extendsbetween said second magnetic flux conductor of the two permanent-magnetmembers. With such a design, the north poles of two secondary magnetsand one primary magnet may all be directed towards, for example, thefirst magnetic flux conductor and the south poles of two secondarymagnets and one primary magnet all be directed towards, for example, thesecond magnetic flux conductor. In this way, the total pole area towardsthe magnetic flux conductors will be large and the magnetic fluxconductors will concentrate the magnetic flux in a direction to or fromthe stator.

According to yet another embodiment of the invention, the magneticdirection of said secondary magnet is essentially perpendicular inrelation to the magnetic direction of the primary magnets. Further, eachmagnetic flux circuit may comprise a magnetic flux that is parallel to aplane which is essentially perpendicular to the movement path. Thedistance between a centre of adjacent permanent-magnet members isadvantageously equal to the distance between a centre of adjacentmagnetic flux conductors in the stator. Further, the magnetic fluxconductors of the stator may then be arranged in an alternating orderwith respect to the direction of the magnetic flux in relation to thepermanent-magnet members in the respective magnetic flux circuit.

According to a still further embodiment of the invention, theessentially closed winding path comprises a second current-carryingsection extending essentially parallel to the movement path. In thisway, a very large part of the essentially closed winding path may beutilized for generation of current and hence the losses are kept at avery low level. Further, the first current-carrying section of thewinding path may be associated with essentially a first half of saidmagnetic flux conductors and the second current-carrying section of thewinding path be associated with an essentially second half of saidmagnetic flux conductors. Preferably, the permanent-magnet members ofthe movable element are adapted to cooperate with those magnetic fluxconductors of the stator which are associated with the firstcurrent-carrying section, and those magnetic flux conductors of thestator which are associated with the second current-carrying section.

According to an additional embodiment of the invention, each magneticflux conductor comprises at least one magnetic flux-conducting section,wherein said sections of each magnetic flux conductor are arranged in aline one after the other which is parallel to the movement path, whereinthe magnetic flux of said sections of each magnetic flux conductorextends essentially in the same direction and wherein a dividing memberis arranged between each pair of adjacent magnetic flux conductors andcomprises main sections that include a magnetically conducting materialand extend along said sections. In such a magnetic flux-conductingdividing member and adjacent sections of the magnetic flux conductors,the magnetic flux will extend in the same direction, which means thatthe magnetic leakage between the magnetic flux conductors may be reducedconsiderably. So-called flux fringing in the stator may thus beessentially prevented. Said sections advantageously form a magneticflux-conducting central section. Further, each magnetic flux conductormay comprise at least said central section and two magneticflux-conducting end sections adjoining an air gap between the stator andthe movable element. Each dividing member is preferably magneticallyinsulating along the end sections, which prevent magnetic leakage causedby the opposite magnetic flux direction of adjacent permanent-magnetmembers of the movable element. The magnetic insulation mayadvantageously be achieved in such a way that each dividing member formsa space with air along the end sections. The main section of saiddividing member may be made of magnetically conducting iron.

According to another embodiment of the invention, the two end sectionsof each magnetic flux conductor are displaced in a plane essentiallyperpendicular to the movement path in relation to the end sections ofeach adjacent magnetic flux conductor.

According to still another embodiment of the invention, the movableelement is adapted to carry out a reciprocating motion. Further, themovable element may be connected to at least one piston that is movablyarranged in a housing. In this case, the electrical machine may bearranged to cooperate with a combustion engine, wherein said housingforms a combustion chamber in which the piston is movable back andforth. The electrical machine may thus be utilized as an electricgenerator, whereby the movement of the piston is substantially achievedwith the aid of a combustion process in a manner known per se. Inaccordance with the principles described in WO01/45977, however,electrical energy may be fed to the stator of the machine to bring aboutan exact positioning of the piston in the housing when the combustion isinitiated. Thus, the electrical machine may serve, besides forgenerating electric power, as a connecting rod for the piston. Theelectrical machine may also be utilized as a pure electric motor, forexample for driving a piston pump.

According to yet another embodiment of the invention, the movableelement is adapted to carry out a rotating movement. Such a rotatingelectrical machine may serve and be utilized as a motor for driving avehicle or some other device. The high power or torque density makes theelectrical machine suitable, for example, as a wheel motor in a vehicle,that is, a motor that is arranged in close proximity to a vehicle wheel.

According to a further embodiment of the invention, the electricalmachine is intended to operate as a generator for generating electricpower. Because of the high torque density, the machine may be drivenrelatively slowly, which is an advantage in many applications, forexample as an electric generator in a wind power plant for a rotatingelectrical machine or as an electric generator in a wave power plant fora linear electrical machine.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be explained in greater detail by meansof various embodiments, which are shown as examples only, and withreference to the accompanying drawings, wherein

FIG. 1 schematically shows a view of a linear electrical machineaccording to a first embodiment of the invention.

FIG. 2 schematically shows a longitudinal section view of part of alinear electrical machine according to the first embodiment.

FIG. 3 shows a cross-section view of a first stator element of a linearelectrical machine according to the first embodiment.

FIG. 4 shows a cross-section view through a second adjacent statorelement of a linear electrical machine according to the firstembodiment.

FIG. 5 shows a perspective view of a stator element and a dividingmember of a stator of an electrical machine according to the firstembodiment.

FIG. 6 shows an exploded view of a permanent-magnet member and twointermediate members of a movable element of an electrical machineaccording to the first embodiment.

FIG. 7 shows a view of the dividing member of FIG. 5.

FIG. 8 schematically shows a view of a rotating electrical machineaccording to a second embodiment of the invention.

FIG. 9 schematically shows a radial section through a first statorelement of a rotating electrical machine according to the secondembodiment.

FIG. 10 schematically shows a radial section through a second statorelement of a rotating electrical machine according to the secondembodiment.

FIG. 11 schematically shows a wind-power application for generatingalternating current with a rotating electrical machine according to theinvention.

FIG. 12 schematically shows a wind-power application for generatingdirect current with a rotating electrical machine according to theinvention.

DETAILED DESCRIPTION OF DIFFERENT EMBODIMENTS OF THE INVENTION

The present invention relates to an electrical machine of thetransversal-flux type. The electrical machine comprises a stator 1 and amovable element 2. FIG. 1 schematically shows a linear electricalmachine 3 according to a first embodiment of the invention with amovable element 2 moving in relation to the stator 1 back and forthalong an essentially rectilinear movement path extending parallel to theaxis a. It should be noted that in this application, the expressionlinear electrical machine also relates to the case where the movableelement 2 moves back and forth along an arched movement path.

FIG. 8 schematically shows a rotating electrical machine 4 according toa second embodiment of the invention with a movable element 2 in theform of a rotor rotating around a centre axis b, the movement pathextending along a circle around the centre axis b. In this case, as inthe arched case above, the term movement path, in the expressions“across the movement path” and “parallel to the movement path”,respectively, means the tangent to the movement path in the position inquestion.

In the following, the first embodiment will first be described withreference to FIGS. 1-7, wherein FIG. 2 only shows a schematiccomposition whereas FIGS. 3-7 show more of a possible design. The stator1 comprises a plurality of stator elements 9, 10 (see FIG. 2) and anelectric conductor that forms a winding 11 extending in an essentiallyclosed winding path, which is schematically indicated in FIG. 1. Thewinding 11 extends through each stator element 9, 10. In the embodimentshown in FIGS. 2-7, the essentially closed winding path comprises afirst essentially rectilinear current-carrying section 12 extendingessentially parallel to the movement path and the axis a, and a secondessentially rectilinear current-carrying section 13 extendingessentially along the movement path and the axis a (see especially FIGS.3 and 4). The two essentially rectilinear sections 12 and 13 areconnected to each other at the ends, as indicated in FIG. 1, the winding11 thus being closed.

The movable element 2 comprises a number of permanent-magnet members 15(see FIGS. 2, 3, 4 and 6), each of which comprising a primary magnet 16.Each primary magnet 16 has a north pole and a south pole and a magneticdirection extending from the south pole to the north pole. Thus, themagnetic direction of the primary magnets 16 extends essentially acrossthe movement path and the axis a, and more precisely essentiallyperpendicular to the movement path and the axis a. As will be clear fromFIG. 2, the permanent-magnet members 15 are arranged in an alternatingorder in the movable element 2 with respect to the magnetic direction ofthe permanent-magnet members 15. Each permanent-magnet member 15 hasessentially the same width. Further, the distance between a centre ofadjacent permanent-magnet members 15 is essentially equal to thedistance between a centre of adjacent stator elements 9, 10 of thestator 1.

In the embodiment shown in FIGS. 3 and 4, each stator element 9, 10comprises two magnetic flux conductors 21, 22 and 23, 24, respectively.Each magnetic flux conductor 21, 22 and 23, 24, respectively, formstogether with one of the permanent-magnet members 15 a closed magneticflux circuit 25, extending around a respective current-carrying section12, 13 of the winding 11 which is indicated by a dashed line in FIGS. 3and 4. Each magnetic flux conductor 25 thus comprises a magnetic fluxthat is parallel to a plane which is essentially perpendicular to themovement path and the axis a.

The electrical machine thus comprises two types of stator elements 9,10. FIG. 3 shows a first type of stator element 9 at the very front ofthe figure with the two magnetic flux conductors 21 and 22. FIG. 4 showsa second type of stator element 10 at the very front of the figure withthe two magnetic flux conductors 23 and 24. FIG. 5 shows the two typesof stator elements 9 and 10 arranged one after the other with a dividingmember 30 therebetween. The dividing member 30 will be explained ingreater detail below.

The first current-carrying section 12 is associated with essentially afirst half of the magnetic flux conductors, that is, the magnetic fluxconductors 21 and 23, whereas the second current-carrying section 13 isassociated with essentially a second half of the magnetic fluxconductors, that is, the magnetic flux conductors 22 and 24. In theembodiment shown in FIGS. 1-7, the electrical machine comprises twomovable elements 2 with permanent-magnet members 15. The first movableelement 2 cooperates with the magnetic flux conductors 21 and 23 and thesecond movable element cooperates with the magnetic flux conductors 22and 24. The magnetic flux conductors 21, 22 and 23, 24, respectively,are arranged in an alternating sequence with respect to the direction ofthe magnetic flux in relation to the permanent-magnet members in therespective magnetic flux circuit.

It should be noted here that the invention is not limited to such anembodiment with two movable elements 2 but it may also be realized withonly one movable element 2, in which case two magnetic flux conductorsextend around a respective current-carrying section and through the samepermanent-magnet members. Such a principle is shown in WO01/78218 (ABBAB) and may very well be applied also to this invention.

The stator 1 further comprises the above-mentioned dividing members 30(see FIGS. 2, 5 and 7). Such a dividing member 30 is arranged betweenessentially each pair of stator elements 9, 10 with magnetic fluxconductors 21-24. Each magnetic flux conductor 21-24 comprises at leastone magnetic flux-conducting central section 26, said sections beinglocated in a line one after the other. This line is parallel to themovement path and to the axis a. The magnetic flux of these magneticflux-conducting central sections 26 of each magnetic flux conductor21-24 extends in essentially the same direction, which is clear fromFIGS. 3 and 4. Each dividing member 30 comprises main sections, which inthe embodiment shown extend along the entire dividing member 30 andwhich comprise a magnetically conducting material, for examplemagnetically conducting iron. The dividing member 30 and the magneticmaterial will thus extend along the magnetic flux-conducting centralsection 26 of the magnetic flux conductors 21-24.

Further, each magnetic flux conductor 21-24 comprises two magneticflux-conducting end sections 27 and 28, which extend inwardly from thecentral section 26 towards the permanent-magnet member 15. Theintermediate dividing members 30 are magnetically insulating along theend sections 27 and 28. This can be achieved by each dividing member 30forming a void or a space with air along the end sections 27 and 28; cf.especially FIGS. 3-5, where the two end sections 27 and 28 of themagnetic flux conductors 21 and 22 are displaced in a plane essentiallyperpendicular to the movement path and the axis a in relation to the endsections 27 and 28 of the adjacent magnetic flux conductors 23 and 24.The space between the end sections 27 and 28 may also be filled with amagnetically insulating material. The magnetic flux in the centralsections 26 of all the magnetic flux conductors 21 and 23 lying oneafter the other and in the main sections of all the dividing members 30arranged therebetween will thus extend in the same direction. Likewise,the magnetic flux in the central sections 26 of all the magnetic fluxconductors 22 and 24 lying one after the other and in the main sectionsof all the dividing members 30 arranged therebetween will extend in thesame direction. In this way, the magnetic leakage between the magneticflux conductors 21 and 23 and between the magnetic flux conductors 22and 24, respectively, will be reduced considerably. So-called fluxfringing in the stator 1 may therefore be essentially avoided.

The movable elements 2 will now be described in greater detail.Essentially each pair of adjacent permanent-magnet members 15 of eachone of the movable elements 2 is separated by an intermediate member 40.Essentially each such intermediate member 40 comprises, in theembodiment shown, two secondary magnets 41 and 42, each of which has anorth pole and a south pole and a magnetic direction extending from thesouth pole to the north pole. The magnetic direction of essentially eachsecondary magnet 41, 42 extends essentially across the magneticdirection of the primary magnet 16, and in the embodiment shownperpendicular to the magnetic direction of the primary magnet 16. Thus,the magnetic direction of the secondary magnet extends essentiallyparallel to the movement path of the axis a.

As is clear from FIGS. 2 and 6, the secondary magnets 41 and 42 of anintermediate member 40 between two adjacent permanent-magnet members 15are arranged in such a way that the first secondary magnet 41 is in thevicinity of the north pole of the primary magnet 16 of onepermanent-magnet member 15 and the south pole of the primary magnet 16of the other permanent-magnet member 15 and such that the secondsecondary magnet 42 is in the vicinity of the south pole of the primarymagnet 16 of one permanent-magnet member 15 and the north pole of theprimary magnet 16 of the other permanent-magnet member 15.

In the embodiment shown, in addition, each permanent-magnet member 15comprises a first magnetic flux conductor 43 on one side of the primarymagnet 16 and a second magnetic flux conductor 44 on the other side ofthe primary magnet 16. In this way, the secondary magnet 41 of anintermediate member 40 between two adjacent permanent-magnet members 15will extend between the first magnetic flux conductors 43 and the secondsecondary magnet 42 between the second magnetic flux conductors 44. Itshould be noted here that the magnetic flux conductors 43 and 44 are notnecessary. The primary magnets 15 may, in this case, extend across thewhole movable element 2, that is, each primary-magnet member 16 consistssolely, or essentially solely, of a primary magnet 15.

Further, each intermediate member 40 of the movable element 2 comprisesa layer 50 of a magnetically insulating material, which extends aroundand encloses the two secondary magnets 41, 42, see especially FIG. 6, inthe intermediate member 40.

FIGS. 8 to 10 show a second embodiment of a rotating electrical machine4. This electrical machine 4 functions in the same way as the electricalmachine 3 in the first embodiment and elements with a corresponding orthe same function have been given the same reference numerals in the twoembodiments. Winding 11 in this embodiment comprises only onecurrent-carrying section 12 extending around the rotor 2 and througheach stator element 9, 10. Each stator element 9, 10 comprises amagnetic flux conductor 21, 23 for a magnetic flux extending in parallelwith an essentially radial plane with respect to axis b. Also therotating electrical machine 4 comprises two types of stator elements 9and 10, which is clear from FIGS. 9 and 10. The magnetic flux conductors21 and 23 form together with a respective permanent-magnet member 15 amagnetic flux circuit 25 extending in parallel with a radial plane. Inprinciple, the permanent-magnet members 15 have the same composition asin the linear machine 3 but are arranged along a circular movement paththat is parallel to a peripheral line of the robot 2. The rotor 2comprises a support member 60 supporting the peripheral permanent-magnetmembers 15. The support member 60 is connected to a shaft 61 thatrotates around an axis of rotation b and that is adapted to transmitmechanical force to or from the rotor 2 and from or to an externaldevice, for example one or more drive wheels 92 of a vehicle (see FIG.1).

FIG. 1 shows how the electrical machine 3 is able to cooperate with acombustion engine comprising a housing 75 and two pistons 76 which aremechanically freely movable in the housing 75. The pistons 76 areconnected to the movable element 2 and may thus move in a rectilinearreciprocating motion in the housing 75 in parallel with theabove-mentioned movement path and with the axis a. The pistons 76 arenot mechanically connected to any element for transmission of force, forexample via a connecting rod and a crankshaft. In the embodiment shown,two pistons 76 are arranged. It is, however, possible to arrange onlyone piston 76 and, for example, replace the second piston by a springelement that attends to the reciprocating motion of the movable element2. The combustion engine may operate according to principles ofcombustion engines known per se. For example, the combustion engine 1may be a two-stroke or a four-stroke Otto engine or diesel engine. Thecombustion engine may also comprise a so-called HCCI (Homogeneous ChargeCompression Ignition) engine which may be regarded as a mixture betweenan Otto engine and a diesel engine, whereby a mixture of oxidizer andfuel is injected into the combustion chamber and ignited at highcompression by self-ignition. In addition to combustion engines withinternal combustion, that is, in the housing 75, the combustion enginemay also comprise external combustion, for example a Stirling engine. Anembodiment relating to an Otto engine, but which is also applicable to aconsiderable extent to other types of motors, will be described in thefollowing. The housing 75 comprises an internal space which in theexample shown forms two combustion chambers 77. For ignition andinitiation of an intermittent combustion in the respective combustionchamber 77, a spark plug 78 may, for example, be arranged. Further, eachcombustion chamber 77 may, where appropriate, comprise valve means 79 orsimilar means enabling supply of fuel and oxidizer as well as removal ofcombustion gases. The mode of operation of the valve means 79 duringoperation of the combustion engine is controlled with the aid of acontrol unit 80 which is also adapted to initiate the supply of voltagepulses to the spark plugs 78 when combustion is to be initiated. Thedevice also comprises schematically shown sensing members 81 for sensingthe position of the pistons 76 in the housing 77. The sensing members 81are connected to the control unit 80.

The control unit 80 is adapted, during operation of the device, tocontrol the direction of the power exchanged between the winding 11 ofthe stator 1 and an external electric circuit. The external circuit maycomprise an energy-storing member in the form of, for example, a battery91, a current consumer in the form of one or more drive motors 4 fordriving wheels 92 of a vehicle 93. The power exchange, which varies withthe time and the movement of the movable element 2, is illustrated inFIG. 1 by the arrows P and P′. As will be clear, the combustion enginewill generate an active power P, the mean value of which, in accordancewith the object of the combustion engine, is considerably greater thanthe active power P′ that is fed back with the aid of the winding 11 ofthe stator 1 to influence and position the pistons 76. The control unit80 is thus adapted to control the magnitude of the power P, P′ in thetwo directions in a continuous manner. It should also be noted that thecontrol unit 80 is dimensioned and adapted for feeding reactive power tothe winding 11 of the stator 1, which is illustrated by the arrow Q. Inthis way, the peak power may be increased by the reactive power Q to agreater or smaller extent achieving the magnetic flux in the winding 11.One advantage of the technique according to the invention is that theneed of reactive power Q from the control unit 80 is smaller than withthe prior art method, that is, the control unit 80 may be made smaller.The control unit 80 comprises a first converter 94 which is connected,with a first connection side, to the winding 11 of the stator 1 via theconnection line 95 and which is connected, with a second connectionside, to a first connection side of a second converter 97 via anelectrical connection. The second converter 97 is connected, with itssecond connection side, to the external circuit, here represented by thedrive motors 4 via the connection lines. The first converter 94 may, forexample, be an AC/DC converter and the second converter 97 a DC/ACconverter. The invention is not limited to these types of converters butthese may be of all types available, that is, AC/DC, DC/AC, DC/DC orAC/AC. With the aid of the converters 94 and 97, the supply of theactive power and of the reactive power is made possible.

Further, the control unit 80 comprises a third converter 99 which isconnected, with a first connection side, to the second connection sideof the first converter 94, and which is connected, with a secondconnection side, to the external circuit, here represented by theenergy-storing member 91. In the example shown, the third converter 99is a DC/DC converter. Also in this case, of course, other types ofconverters may be used. The converters 94, 97 and 99 comprise powerelectronics, preferably with diodes and IGBT valves. It should also benoted that two or three of the converters 94, 97 and 99 may constitutean integrated converter unit.

In addition, the control unit 80 comprises a computer 100, with one ormore microprocessors, at least one memory unit and suitable members forcommunication. The computer 100 is adapted to control the converters 94,97 and 99 for exchange of the active power and the supply of thereactive power to the winding 11 of the stator 1. Further, in theexample shown, the computer 100 is connected to the spark plugs 78 andthe valve members 79. The computer 100 receives signals from a largenumber of different sensors and sensing members of the combustion engine1 and the vehicle. In the example shown, this is illustrated by theposition-sensing member 81 only. With the aid of signals from thevarious sensing members and with the aid of software, the combustionengine and its mode of operation are illustrated in the computer 100.This software may be stored in the computer 100 or be received from anexternal computer source via some data communication system.

It should be noted that a corresponding control unit 80 may also beutilized for controlling power to and from the rotating electricalmachine 4 according to the second embodiment.

FIG. 11 schematically shows how the rotating electrical machine 4 inFIGS. 8-10 may be utilized in an application for generating alternatingcurrent in a wind power plant. The electrical machine 4 is connected,via the shaft 61, to a wind power propeller 110. A gearbox 111 maypossibly be arranged between the propeller 110 and the electricalmachine 4 for adjusting the speed. The electrical machine 4 may beconnected into an electric ac network 112.

FIG. 12 schematically shows, in a manner similar to that in FIG. 11, howthe electrical machine 4 in FIGS. 8-10 may be utilized in an applicationfor generating direct current in a wind power plant. Here, theelectrical machine 4 may be connected to an electric dc network 113,possibly via suitable rectifier equipment 114.

The invention is not limited to the embodiments shown but may bemodified and varied within the scope of the following claims.

1. An electrical machine of the transversal-flux type, comprising astator comprising a plurality of stator elements with magnetic fluxconductors and an electric conductor forming a winding extending in anessentially closed winding path through each magnetic flux conductor,and a movable element which comprises a number of permanent-magnetmembers and which is movable in relation to the stator along a movementpath, wherein the movable element is adapted to carry out a linearreciprocating motion, wherein the essentially closed winding pathcomprises a first current-carrying section extending essentially alongthe movement path, wherein each magnetic flux conductor is adapted toform, together with one of said permanent-magnet members, a closedmagnetic flux circuit extending around said current-carrying section,wherein each permanent-magnet member comprises a primary magnet that hasa north pole and a south pole and a magnetic direction extending fromthe south pole to the north pole and essentially across the movementpath, and wherein the permanent-magnet members are arranged in analternating order in the movable element with respect to the magneticdirection of the primary magnet, characterized in that adjacentpermanent-magnet members of the movable element are separated from eachother by an intermediate member comprising at least one secondary magnetwhich has a north pole and a south pole and a magnetic directionextending from the south pole to the north pole and essentially acrossthe magnetic direction of the primary magnet, wherein magnetic fields ofadjacent permanent-magnet members and their secondary magnets areoperable to mutually repel for essentially avoiding flux fringing inrespect of the stator.
 2. An electrical machine according to claim 1,characterized in that the magnetic direction of the secondary magnetextends essentially parallel to the movement path.
 3. An electricalmachine according to claim 2, characterized in that each intermediatemember of the movable element comprises two secondary magnets.
 4. Anelectrical machine according to claim 3, characterized in that secondarymagnets of an intermediate member between first and second adjacentpermanent-magnet members are arranged in such a way that the firstsecondary magnet is in the vicinity of the north pole of the primarymagnet of the first permanent-magnet member and the south pole of theprimary magnet of the second permanent-magnet member and so that thesecond secondary magnet is in the vicinity of the south pole of theprimary magnet of the first permanent-magnet member and the north poleof the primary magnet of the second permanent-magnet member.
 5. Anelectrical machine according to claim 3, characterized in that eachintermediate member of the movable element comprises a layer of amagnetically insulating material outside the two secondary magnets. 6.An electrical machine according to claim 3, characterized in that eachpermanent-magnet member comprises a first magnetic flux conductor on oneside of the primary magnet and a second magnetic flux conductor on theother side of the primary magnet.
 7. An electrical machine according toclaim 3, characterized in that the secondary magnets of an intermediatemember between two adjacent permanent-magnet members are arranged insuch a way that the first secondary magnet extends between a firstmagnetic flux conductor of the two permanent-magnet members and so thatthe second secondary magnet extends between a second magnetic fluxconductor of the two permanent-magnet members.
 8. An electrical machineaccording to claim 1, characterized in that the magnetic direction ofsaid secondary magnet is essentially perpendicular in relation to themagnetic direction of the primary magnets.
 9. An electrical machineaccording to claim 1, characterized in that each magnetic flux circuitcomprises a magnetic flux that is parallel to a plane which isessentially perpendicular to the movement path.
 10. An electricalmachine according to claim 1, characterized in that the distance betweena centre of adjacent permanent-magnet members is essentially equal tothe distance between a centre of adjacent magnetic flux conductors ofthe stator.
 11. An electrical machine according to claim 1,characterized in that the magnetic flux conductors of the stator arearranged in an alternating order with respect to the direction of themagnetic flux in relation to the permanent-magnet members in therespective magnetic flux circuit.
 12. An electrical machine according toclaim 1, characterized in that the essentially closed winding pathcomprises a second current-carrying section extending essentiallyparallel to the movement path.
 13. An electrical machine according claim12, characterized in that the first current-carrying section of thewinding path is associated with essentially a first half of the magneticflux conductors of the stator and the second current-carrying section ofthe winding path is associated with essentially a second half of themagnetic flux conductors of the stator.
 14. An electrical machineaccording claim 13, characterized in that the permanent-magnet membersof the movable element are adapted to cooperate with those magnetic fluxconductors of the stator which are associated with the firstcurrent-carrying section, and those magnetic flux conductors of thestator which are associated with the second current-carrying section.15. An electrical machine according to claim 1, characterized in thateach magnetic flux conductor comprises at least one magneticflux-conducting section, wherein said sections of each magnetic fluxconductor are arranged in a line one after the other which is parallelto the movement path, wherein the magnetic flux of said section of eachmagnetic flux conductor extends in essentially the same direction andwherein a dividing member is arranged between each pair of adjacentmagnetic flux conductors and comprises main sections which comprise amagnetically conducting material and which extend along said section.16. An electrical machine according to claim 15, characterized in thatsaid sections form a magnetic flux-conducting central section.
 17. Anelectrical machine according to claim 16, characterized in that each amagnetic flux conductor comprises at least said central section and twomagnetic flux-conducting end sections.
 18. An electrical machineaccording to claim 17, characterized in that each dividing member ismagnetically insulating along the end sections.
 19. An electricalmachine according to claim 18, characterized in that each dividingmember forms a space with air along the end sections.
 20. An electricalmachine according to claim 1, characterized in that the main section ofsaid dividing member is made of a magnetically conducting iron.
 21. Anelectrical machine according to claim 1, characterized in that the twoend sections of each magnetic flux conductor are displaced in a planeessentially perpendicular to the movement path in relation to the endsections of each adjacent magnetic flux conductor.
 22. An electricalmachine according to claim 1, characterized in that the movable elementis connected to at least one piston that is movably arranged in ahousing.
 23. An electrical machine according to claim 22, characterizedin that the electrical machine is adapted to cooperate with a combustionengine, whereby said housing forms a combustion chamber in which thepiston is movable back and forth.
 24. Use of the electrical machineaccording to claim 1 as a generator for generating electric power. 25.Use of the electrical machine according to claim 1 as a generator forgenerating electric power, said generator being adapted to constitute acomponent in one of a wind power plant and a wave power plant.
 26. Useof the electrical machine according to claim 1 as a motor for generatingmechanical power.
 27. Use according to claim 26, wherein said motor isadapted to form a drive motor in a vehicle.